I love the idea of using the newer LS1 style injectors on our TPI's in fact I just finished buttoning up my own set to the rails. This is just a strong recommendation, but to make some sense out of it here's the back story. The lS1 injectors are shorter than the standard body old style injectors. Some people will tell you you can run them without any leaks and this is for the most part true. However a friend of mine ran a set of LS1 injectors on his LT1 Trans Am and DID develope a leak because one finally scooted down into the intake a little resulting in a pretty serious fuel leak. Now for us TPI guys there's an easy solution for installing the LS1 injectors to our rails. Get a dremel with a heavy duty cut off wheel, set it on low speed and go around the 2 spots in the injector ring basically making the ring go all the way around the injectors. Don't worry when some plastic bubbles up, just take a razor blade and clean up the cuts. This will allow you to place the clips from your original TPI injectors onto your new LS1 injectors and mount them properly to the rails. I've attached a pic below of 2 of my installed injectors.

I ran them on my TPI, and now miniram with no clips and no leaks. I just put them in the bore first then bolt down the fuel rail. 10K miles and no problems.

i know your precautions are valid but i also ran em with no clip..........doing fine.

I wouldn't have posted this up had I not seen one of them pull out. It only takes 1 time to end up without a car. This is for anyone who has them out and is going to install them, in my mind it's worth the extra 1/2 hour to do it this way. I had actually planned to just install them without the clips after reading several people who said it wasn't an issue, but when my friends TA pulled that I said "no way" and finished them up. Seriously the ammount of fuel a high volume fuel pump dumps in 20 seconds is amazing. He had gas EVERYWHERE.

You make a very valid point and also a very good tech tip. Are the LS1 injector connectors the same as the TPI.

TRUE THAT!!!!!!!!!!!!!!!!!

Sorry for the late response, yes the clips are identical they snap right in. The injectors seat in the rails with no issues, no leaks around the O rings. The only thing I've noticed about these injectors is that they're louder than the old ones. Small price to pay for far newer, better designed injectors that flow more than my old ones did.

I was just thinkin without lookin at my intake but couldnt you just machine the 4 fuel rail mounting bosses to make up for the length

If you want the injectors to seat deeper into the manifold, simply grind off a little of the mounting points. 1/8 to 1/4in should do it but it's unnecassary. I didn't grind it down because I didn't want to run into any fuel rail interferance but other members have done this.

whats the flow rate of the LS1s?

Is the resistance in the LS1 injectors different from the stock?
I have a set of LS1 #26 and I measure the resistance to 11.9 ohm, all injectors. Stock injectors are 16.2 ohm.
Is the 11.9 ohm correct?
Will I run into any problems with the injecting system if I mount these injectors with a lower resistance?

The larger LS1 injectors flow 25 pounds at 3 bar 28 pounds at 4 bar. The resistance is the same, they run just fine. I don't know why your old injectors are running 16 ohm, mine ran 11 to 13.

The LS1 injectors are about 0.12" shorter than our 3rd gen injectors. I have both types of cars and have posted the lengths on here. The best solution is posted above. Simply cut down the 4 posts that the fuel rail mounts to by 0.1". You should always run the locking ring to secure the injectors into the fuel rail properly. And of course, use a lubricate on the O-rings.